802.1X is an IEEE standard for port-based network access control that provides authentication framework to prevent unauthorized devices from accessing network resources until proper credentials are validated. It operates using the Extensible Authentication Protocol (EAP) to facilitate secure communication between supplicants (client devices), authenticators (network switches), and authentication servers (typically RADIUS). The 802.1X framework supports various authentication methods including username/password, digital certificates, and smart cards, enabling organizations to implement comprehensive network access control policies with granular user and device identification capabilities.